Add P300 fixture (#717)

* Add P300 fixture

* fixture after update

* Add tests for p300

kasa/tapo/__init__.py

@@ -1,6 +1,7 @@
 """Package for supporting tapo-branded and newer kasa devices."""
+from .childdevice import ChildDevice
 from .tapobulb import TapoBulb
 from .tapodevice import TapoDevice
 from .tapoplug import TapoPlug
 
-__all__ = ["TapoDevice", "TapoPlug", "TapoBulb"]
+__all__ = ["TapoDevice", "TapoPlug", "TapoBulb", "ChildDevice"]

kasa/tapo/childdevice.py

@@ -35,7 +35,7 @@ class ChildDevice(TapoDevice):
                     return child
 
             raise SmartDeviceException(
-                f"Unable to find child device with position {self._id}"
+                f"Unable to find child device with id {self._id}"
             )
 
         self._last_update = self._sys_info = self._info = _get_child_info()